1. Technical Field
The present disclosure relates to a printed circuit board, and particularly to a printed circuit board with compound via.
2. Description of Related Art
With enhancement of data transmission speeds, the integrity of transmitted signals has become a priority in successful data transmission, as well as an essential consideration in the design of PCBs (printed circuit board). Factors such as the type of electronic components, the related parameters of the PCB, and the layout of the electronic components thereon can affect the integrity of transmitted signals. As a result, identification of affecting factors and what methods can be employed to minimize their effects effectively are critical. For PCBs, such factors include matching and continuity of impedance. If the impedance is not continuous, the quality of signals will be affected, and the efficiency of the entire system affected.
With concentration on minimization of device size and profile, via-on-pad structure is utilized in the PCB which has coexistence/in-coexistence wiring structure for high speed signal transmission. That is, a via is formed on an AC-coupling capacity pad to conserve wiring space. However, in comparison with transmission wires, the pads with via formed thereon exhibit greater electric capacity and lower impedance which present as impedance discontinuity. Consequently, the quality of the signals is affected. Particularly, with the increment of signal transmission speed in recent years, the problems caused by impedance discontinuity have become increasingly obvious.